1. Field of the Invention
The invention is related to the detection of pancreatic lipase. More specifically, the invention relates to pancreatic lipase polypeptides, polynucleotides encoding the polypeptides; antibodies specific for the polypeptides, and method of using the polypeptides and antibodies to detect pancreatic lipase in biological samples.
2. Description of Related Art
Complete citations to the references described herein by author and date are provided in the Bibliography section at the end of the specification.
Lipases are water-soluble enzymes that hydrolyze water-insoluble substrates into more polar lipolysis products (Petersen and Drablos 1994). A plethora of lipases have been identified in microorganisms, plants, and animals (Lin et al., 1986; Jaeger et al., 1994; Petersen and Drablos, 1994; Mukherjee and Hills, 1994; Lawson et al., 1994). Lipases share a common triad of amino acids (serine, aspartic or glutamic acid, and histidine) in the active site, which is also shared with serine proteases (Svendsen, 1994). Another common feature of almost all lipases are glycosylation site motifs (Antonian, 1988). Many lipases have been shown to be related phylogenetically. The pancreatic lipase gene family is a large gene family with 9 subfamilies (Petersen and Drablos, 1994; Carriere et al., 1997; Carriere et al., 1998; Hirata et al., 1999). In addition there are other groups of phylogenetically related lipases, and yet other lipases that do not belong to a defined gene family (Anderson and Sando, 1991).
The main function of lipases is the hydrolysis of lipids. A lipase is needed whenever an apolar lipid needs to cross a biological membrane. Triglycerides are prime examples of apolar lipids. Thus lipase is needed in order for triglycerides to be absorbed from the intestinal tract. There are two digestive lipases in most vertebrate species, i.e., a preduodenal lipase and classical pancreatic lipase (Carriere et al., 1994). Preduodenal lipase has been shown to originate from a single tissue in all species examined to date (Moreau et al., 1988). A pharyngeal lipase was identified in cows and sheep, a lingual lipase in rats and mice, and a gastric lipase in human beings, monkeys, horses, pigs, guinea pigs, cats, and dogs (Moreau et al., 1988). No preduodenal lipase could be identified in chickens (Moreau et al., 1988). In human beings and dogs it has been shown that gastric lipase contributes significantly to the digestion of dietary triglycerides (Carriere et al., 1993a; Carriere et al., 1993b). However, pancreatic lipase (also called classical pancreatic lipase) is the most important enzyme in the digestion of dietary triglycerides (Carriere et al., 1991; Carriere et al., 1993a).
It has recently been shown by immunolocalization that pancreatic lipase is only in pancreatic acinar cells in clinically healthy dogs, suggesting that classical pancreatic lipase may be an ideal marker for function and pathology of the exocrine pancreas (Steiner et al., 2002). This hypothesis has been confirmed in clinical studies that have shown that the measurement of pancreatic lipase immunoreactivity in serum is a specific marker for exocrine pancreatic function and also highly sensitive for pancreatitis in the dog (Steiner et al., 2001a; Steiner et al., 2001b; Steiner et al., 2001c).
Pancreatic lipase has an approximate molecular weight of 50 kilodaltons. The purification of classical pancreatic lipase has been reported in many species (Vandermeers and Chroistophe, 1968; Rathelot et al., 1981; Bosc-Bieme et al., 1984; Gieseg et al., 1992; Mejdoub et al., 1994; Steiner and Williams, 2003).
Clinical symptoms of pancreatitis are non-specific and the disease can be difficult to diagnose. Pancreatitis is associated with an increased amount of digestive enzymes and zymogens leaking into the blood stream. One of these enzymes is pancreatic lipase. A number of assays have been developed to detect the presence of lipase in serum by use of catalytic assays. However, these assays lack both sensitivity and specificity for pancreatitis in both human beings and dogs. Accordingly, what is needed is a simple and rapid method and device for sensitively and specifically detecting pancreatic lipase.